44 AYERS. [Vol. VI. 



meshes of the network are relatively wide, usually oval in shape, 

 with the long axis of the oval parallel with the course of the 

 auditory hairs, which in the membrane are glued together in 

 bands separated incompletely by the interspaces. The mem- 

 brana Cortii is characterized by radial striations, while the 

 " membranes " over the maculae utriculi and sacculi are more 

 loosely put together, and appear to be made up of a network 

 of fine fibres. These fibres anastomose freely and are struc- 

 tureless and hyaline under ordinary powers of the microscope. 

 With requisite treatment and sufficiently high powers the 

 meshes of the network are seen to be composed of bundles 

 of fibrillas. The otolithic crystals are supported on the upper 

 surface of the tectorial membrane and are disposed in several 

 layers. How they are retained in place is not apparent. The 

 extreme edges of the membrane are free from the crystals. 



OTOLITHS, OTOCONIE. 



Otolithic calcareous matter is deposited in the ears of all ver- 

 tebrate animals. It is precipitated out of the lymph at first in 

 the form of small granules usually crystalline. These primary 

 otoliths grow as all crystals grow when immersed in solutions 

 containing their salts under proper chemical and physical con- 

 ditions. The calcareous salts are supplied in two quite different 

 ways. The first and probably the most important source in the 

 adult ear is the lymph which, passing from the blood-vessels 

 into the cavity of the internal ear, contains the calcareous salts 

 in solution. The second and probably most important source 

 of calcareous matter during embryonic life is the auditory epi- 

 thelium which during its passage through the ontogenetic stages 

 of its development exerts one of its phylogenetic functions, that 

 of calcareous secretion, for dermal purposes. This embryonic 

 activity gradually gives way as the adult functions of the cells 

 become more and more pronounced. 



The otoliths of the vertebrate ear are then by nature foreign 

 bodies, just as renal and vesical calculi are, though of course 

 there are certain differences in the conditions leading up to 

 their production in the different organs. Those vertebrate 

 forms which retain most of the primitive relations of the audi- 

 tory organs deposit most calcareous matter {e.g. Sharks, Skates), 



